Ultimate Marathon Long Run Guide: How Long Should Your Long Run Be? - Lee Grantham

Aug 13, 2025

Intro

This is a quick summary of “Ultimate Marathon Long Run Guide: How Long Should Your Long Run Be?” from Lee Grantham. It’s a great watch — we’re breaking it down so you can try the workout today. Be sure to check out the full video for all the details.

Key Points

Long runs serve three purposes: physical strength, physiological endurance (heart, lungs, aerobic capacity) and mental resilience for the marathon.
Train at your target marathon pace (e.g., 5 min/km) and also spend time at 10 % faster (≈4:30 /km) and 10 % slower (≈5:30 /km) paces to make the marathon pace feel easy.
Use the long run to test fueling, practice race‑day terrain, and fine‑tune recovery; treat it as a feedback session for core strength and fatigue management.
Build a 13‑week specific training block (10 weeks of long runs + 10 interval sessions) plus 3 weeks of taper; aim for at least 80 % of those sessions to be on‑target for a PB.
Benchmark race (10‑13 mi or 10‑13 km) a few weeks out at marathon pace can boost confidence and simulate race‑day nutrition and pacing.

Workout Example

Goal: Feel comfortable at marathon pace (5 min/km) by training with a 24 km long run.

Warm‑up: 5 km at 5:30 /km (10 % slower) – easy, builds endurance.
Main set: 14 km at 5:00 /km (your target marathon pace) – the core marathon‑pace block.
Finish: 5 km at 4:30 /km (10 % faster) – teaches the body to handle faster surges.

Optional interval work (once per week): 3‑4 × 5 min intervals at 3:00–3:20 /km (10 %–20 % faster than marathon) with 2 min easy jogs in between. This builds speed while keeping the marathon pace feeling easy.

Closing Note

Give this long‑run structure a try and tweak the paces to match your own marathon goal in the Pacing app. You’ll build confidence, strength and the mental toughness you need on race day. Happy running!